I'm new to APEX but I have been using Oracle Forms for a while. I created an interactive report link to a dml form to create a simple file maintenance.

The Apex DML form that got created from a wizard displays all the columns vertically (1 row for each column). I want to re-arrange this so that some columns are in 1 row and some are not and also some columns are not all aligned. Please see below for a sample layout concept that I want to do

What is the best way to do this in Apex? Is this possible using Grid Layout? Also is there a GUI interface like in Oracle Forms Layout Editor that I can use in APEX or any third party product?

With APEX we're also fortunate to have a great resource in apex.oracle.com where we can reproduce and share problems. Reproducing things there is the best way to troubleshoot most issues, especially those relating to layout and visual formatting. If you expect a detailed answer then it's appropriate for you to take on a significant part of the effort by getting as far as possible with an example of the problem on apex.oracle.com before asking for assistance with specific issues, which we can then see at first hand.

The Apex DML form that got created from a wizard displays all the columns vertically (1 row for each column). I want to re-arrange this so that some columns are in 1 row and some are not and also some columns are not all aligned. Please see below for a sample layout concept that I want to do

What is the best way to do this in Apex? Is this possible using Grid Layout?

There's only 2 (sane) ways to do this in APEX, using either HTML tables or CSS grid layout. This is determined by the page template, so to know which applies it is necessary to know the theme, page template and Grid Layout Type used.

Also is there a GUI interface like in Oracle Forms Layout Editor that I can use in APEX or any third party product?

Suggestion, dump, run away from and bury if at all possible IE 8... Better to use a browser like Firefox or chrome.. Just a suggestion since they follow css and html 5 standards better than IE ever will..